How to make congealed pork's blood?

So I'm trying to make Chao Huyet Heo (congealed pork blood congee) and I couldn't find the already congealed pork blood but amazingly enough I was able to get my hands on some frozen pork's blood. How do you go about changing it to the liquid form to the jiggly solid form?

Growing up in Hawaii I remember my family, and relatives "making their own meat". This was my Mother's explanation to my brother and I as kids. Lol. I recall that adding vinegar, and salt to the fresh blood while stirring caused it to coagulate. Haven't had 1st hand experience but that's what I recall.